Advanced high efficiency mainsail

ABSTRACT

A sail comprising a rotating flexible mast sleeve wrap surrounding the mast and attached to a sail track for controlling the movement of the sail. The sleeve assembly is slotted to allow for partial rotation of the sleeve wrap, the sail track and the sail, so that the sleeve wrap, the sail track and the sail rotate to form an aerodynamic shape on the lee side of the rotating flexible mast reducing aerodynamic losses.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of the earlier filing date and priority to U.S. provisional application Ser. No. 63/067,310, filed on Aug. 18, 2020, the content of which is hereby incorporated by reference herein in entirety.

TECHNICAL FIELD

The subject matter described herein, relates to additions to fixed masts and booms and or mainsails in order to significantly improve a mainsails efficiency.

BACKGROUND

Mainsails with traditional fixed masts with stays and booms have very poor efficiency. Wind tunnel testing of sails with fixed masts sailing upwind and reaching have shown that ˜15% is lost at the head of the sail, ˜30% (or even 40% if there is a gap between mast and sail) is lost at the mast to sail connection, and ˜25% is lost at the foot.

The lee or backside of the mast to sail connection of a traditional fixed mast forms a pocket of air which prevents laminar flow from the mast to the sail which laminar flow on the lee side of a sail is most important for efficiency. This prevention of laminar flow on the lee side, upon which drive relies, causes this ˜30% loss (being for a round mast with no gap between mast and sail). If a gap is present and mast is oval, then this loss can be up to ˜40%. These figures are in comparison to an airfoil shaped mast which rotates.

This traditional fixed mast and sail arrangement described above, is analogous to a permanently stalling vertical wing. Efficient airfoil shaped rotating masts however are not practical for the majority of sailing boats. Traditional booms used in the majority of sailboats, are mostly situated well above decks and coach houses, this allows low-pressure air from the lee side to leak to the high-pressure windward side under the boom creating a drag rotor and results in a 25% loss of efficiency and drive. Such a sail is similar to a vertical wing. If an aircraft were to use a traditional fixed mast and boom arrangement as do sailboats, it could not take off.

SUMMARY

It is the object of this invention to provide a means to largely eliminate the mast to sail and under boom losses detailed above, by providing a simple practical means which can be applied to the majority of sailing boats and which does not require significant changes to traditional fixed stayed masts and booms.

This application will show how an aerodynamic rotating fairing can be added to a fixed stayed masts and how an aerodynamic skirt can be attached below booms, to eliminate the majority of inefficiency now present in a large majority of sailing boats.

These improvements in efficiency outlined in this application, also give the mainsail drive which is lower and further forward than a traditional fixed mast mainsail, allowing a smaller more easily handled mainsail to be used, while also allowing for a lighter stiffer boat and a boat which is able to point higher.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a cross section of one method of achieving a rotating airfoil mast sail connection.

FIG. 2 shows a cross section of another method of achieving a rotating airfoil mast sail connection.

FIG. 3 shows a cross section of a third method of achieving a rotating airfoil mast sail connection.

FIG. 3A shows a cross section of an alternative to FIG. 3 of achieving a rotating airfoil mast sail connection.

FIG. 4 shows an elevation of a typical fixed mast sailboat with a mast fairing and skirt.

FIG. 5 shows a section through skirt of FIG. 4.

FIG. 6 shows a partial elevation of a boat with a mainsail and skirt.

FIG. 7 shows an isometric part detail of a sail head to halyard connection.

FIG. 8 shows an alternate isometric part detail of a sail head to halyard connection.

FIG. 9 shows another alternate isometric part detail of a sail head to halyard connection.

FIG. 10 shows yet another alternate isometric part detail of a sail head to halyard connection.

FIG. 11 shows an isometric part detail of a sail head to halyard connection.

FIG. 12 shows an isometric part detail of a mainsail tack connection method.

FIG. 13 shows an isometric part detail of an alternative mainsail tack connection with a roller furling boom.

FIG. 14 shows an isometric part view of another tack connection method

FIG. 15 shows a partial cross section of a rotating sliding car or slug to sail connection assembly.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 shows a mast cross section 100 with mast 102 and a mast fairing wrap 101. A sail track 104 connects to fairing 101 via bolt rope connection means 105A and a screwed connection at 105B. Any other normal other connection such as rivet, adhesive, etc., is also possible. Fairing 101 wraps around a typical oval mast 102. Note a round mast shown dotted at 116 or any shaped mast can also be used.

A sail 106 is shown connected to sail track assembly 104. Twin optional bolt rope connections and wraps shown dotted at 114A and 114B are also possible in place of the single mast wrap 101. Fairing wrap 101 would be a flexible member, which easily deforms to rotate around an oval or other mast shape. A secondary wrap shown dotted at 112 and battens, shown dotted at 110A and 110B could be added if desired in order to more rigidly contain wrap 101 and sail track 104 on mast 102. Wrap 112 could be connected to wrap 101 using hook and loop fastening.

Spaced brackets shown dotted at 107 could also be used to secure position of sail track assembly 104. Note, although bolt rope sail tracks are shown for simplicity, any type of sail track can be used. Wind direction is shown by arrow 118. Fairing wrap 101 allows airflow to smoothly travel around back, lee side, of mast shown by arrow 120 so that laminar flow is largely maintained over the lee side of the sail, in order that the maximum efficiency is obtained, and the ˜30% to ˜40% traditional mast to sail losses are eliminated.

It is intended that the sail track 104 would be close the mast at the top and approximately as shown in figure two at the bottom, by using a tapered flexible fairing wrap 101. The fairing wrap 101 would also have slots, appropriately placed to account for spreaders and other items attached to a mast, when the fairing assembly 100 rotates.

Although almost any mast profile will allow this rotation, the optimal mast section profile has a smaller radius at the front shown at 117 compared to the radius at the rear, which ideally is semi-circular. This configuration allows rotation of the sail track at the rear and gives an improved aerodynamic profile on the lee side of the mast. Note front radius 117 can be in the form of an ellipse or a parabola. In this way, a relatively simple connection is achieved, while allowing an aerodynamically efficient mast sail connection.

FIG. 2 shows a typical oval mast section 200, according to another method of providing a simple and more efficient aerodynamic mast to sail connection. This second method allows for a standard sail track fixed to a non rotating mast to be used. As shown, a fixed oval mast 202 with a bolt rope sail track 203 and sail 204. Note any reasonably shaped mast and any style of mast track can be used.

Surrounding mast is a semi-circular bracket 212 which holds two vertical members or fairing pieces 206A and 206B, which are connected to bracket 212 at its outer ends. Bracket 212 would be ideally one of a number spaced along mast 202 whilst fairing pieces 206A and 206B would run between them. Brackets 212 and fairing pieces 206A and 206B would be free to rotate around mast 202.

For a typical mast which is not round, a spacer 214 or spacers shown at 214A and 214B could provide the effect of a round mast allowing bracket 212 and firing pieces 206A and 206B to readily rotate. Spacers 214A and 214B are optional and provide an optimal reliable rotation around a non-circular mast, but are not indispensable.

Spacers 214A and 214B may be fixed along the mast 202 to coincide with brackets 212. Alternatively, brackets 214A and 214B could be floating on mast and loosely retained by brackets 216 and 212. A bracket 216, optional according to certain aspects could be provided to contain rotating bracket 212. If bracket 216 is not used, a tensioning line would be required top and bottom to keep a wrap 208 against mast 202.

Also shown dotted at 216B is a restraining tension member which would attach to either mast or bracket 214. These tensioning lines would preferably be attached to each side of bracket 212, both at the top and bottom. If used, bracket 216 would be attached to a spacer or spacers 214A and 214B. using in one option, attachment bolt holes shown at 215. Bracket 216 could also be of a flexible or fabric material, attached to top and bottom of spacers 214A and 214B.

An aerodynamic wrap 208 attaches to each of the members or fairing strips 206A and 206B and wraps around mast between bracket assemblies 212. Note fairing members 206A and 206B are optional, since wrap 208 could connect directly to brackets 212. Assemblies of brackets 212 would be spaced along the mast 202 with wrap 208 and fairing pieces 206A and 206B between them.

Since assemblies with bracket 212 would be relatively thin and would be spaced well apart, the majority of the mast would have a rotating flexible aerodynamic wrap 208 and fairing pieces 206 A and B to provide an aerodynamic rotating fairing on a fixed mast. In certain embodiments, fabric wrap 208 could have battens shown dotted at 207A and 207B attached to bracket 212, replacing fairing pieces 206A and 206B with fabric wrap 208 between battens, as long as the wrap is tensioned top and bottom.

The fairing assembly 200 may extend from the top area of the sail to a position above the boom, with a gap between fairing and boom, to allow for flaking of the mainsail. Alternatively, if the fairing assembly was required to extend close to the boom shown at 406A in FIG. 4. A removable or unfolding flexible or rigid fairing could be used to allow for flaking could be provided. Wind direction is shown at 218. Airflow around the lee side of sail 202 is shown by arrow 220.

In accordance with one or more aspects, the aerodynamic rotating fairing assembly 200 causes lee airflow to be largely laminar around mast and sail, as shown by arrow 220, eliminating the majority of the ˜30% to ˜40% loss of a traditional mainsail, thus allowing a much more efficient, higher pointing mast and mainsail which can be smaller, lighter and more easily managed while still providing increased efficiency drive and performance.

Note bracket 212 is shown with outer portion 212A being cam shaped. This allows fairing to retain its shape when rotating, since if the mast is not round the fairing would become looser as it rotates from its central position, this cam action against bracket 216 allows aerodynamic fairing wrap to retain its shape. Please also note, bracket 216 could also be flexible in nature.

FIG. 3 shows a cross-section of a typical mast with an alternative rotating aerodynamic fairing assembly 300 in which the sail track 306 is not fixed directly to mast 302 but can rotate. FIG. 3 has mast section 302 with a bracket 304 and sail 308. Two rigid or semirigid fairings 310A and 310B are attached to the bracket 304. A sail track 306 is also attached to the bracket 304, a bolt rope type sail track is shown for simplicity, however here and elsewhere, any type of sail track can be used.

It should also be noted that sail track 306 may also be independently rotating on mast 302, rather than being attached and rotating with bracket 304. This is achieved in one method, by sail track 306 being attached to a separate wrap shown dotted at 311. It should be further noted that a sail track could be attached directly to the fairings 310 A and B, shown dotted at 306A, in place of sail track position 306. Alternatively a mainsail 308A could be attached to a furling tube shown dotted at 309, attached top and bottom to bracket or brackets 304.

A flexible wrap is shown at 312 wrapping around mast 302 with each end fastened to fairings 310 A and B. The flexible fairing wrap 312, could alternatively wrap around mast to positions 307A and 307B with 310A and 310B being spaced battens. Spaced battens in this case, would be connected to a bracket 304. In its simplest form, if aerodynamic fairing wrap 312 is tapered, with the top being least in circumference, then only one batten at the bottom would be required, and no brackets would be necessary.

If a flexible wrap and at least one batten is used, then wrap would be tensioned by lines top and bottom. This flexible wrap and batten system could also be an alternative construction for the previous arrangements of FIGS. 1 and 2. Note also that fairing members 310A and 310B are optional. Bracket 304 could extend to position shown by 307A and 307B or to sail track 316A and connect directly to the flexible wrap, if wrap member is tensioned top and bottom.

In this way, a simple efficient rotating aerodynamic fairing can be provided which rotates around the majority of a fixed mast. Slots would be provided in the rotating fairing where necessary to allow for spreaders and other mast attachments. The assembly 300 would cover the majority of the mast above the boom, while bracket 304 could be the same length as the fairings or be of narrow depth and be spaced along the mast at appropriate intervals.

The fairing assembly bottom 300 would extend to a position above the boom, shown at 406A in FIG. 4, to allow for flaking of the mainsail. Alternatively, if the fairing assembly was required to extend close to the boom, a removable or unfolding flexible or rigid fairing close to the boom could be used to allow for flaking. A wind direction is shown at 314. Airflow around the lee side of the mast 302 is shown by arrow 316. This aerodynamic rotating fairing assembly 300, causes lee airflow to be largely laminar around the lee side of the mast and sail, shown by arrow 316, eliminating the majority of the ˜30% to ˜40% loss of a traditional mainsail, thus allowing a much more efficient, higher pointing mainsail and mast which can be smaller, lighter and more easily managed while still providing increased efficiency, drive and performance.

Bracket 304, fairings 310A and 310B and sail track 306 or 306A are shown as separate pieces which would be screwed, glued or bolted together, if sail track 306 is not separately rotating, but it is possible to construct these four pieces as one length or short lengths for ease of construction and shipping and then connected together. The preceding has shown how a large portion of the inefficiency of a mainsail may be significantly reduced or largely eliminated at the traditional fixed mast sail connection, but this still leaves a significant loss at a traditional boom.

FIG. 3A shows a part section of a rotating firing assembly 320, with mast 321 and rotating bracket 324, similar to that of FIG. 3, except that sail 328 has a double luff which connects to fairing strips 322A and 322B. one side of sail luff 328 connects to fairing strip 322A via a roller sail track, while the other side of sail luff connects to luff strip 322B via a bolt rope sail track 330. As in FIG. 3, note, any type of sail track can be used and would usually be the same on both sides. A flexible wrap extends from fairing strip 322A to 322B, in order to provide a rotating fairing assembly which is highly efficient. In some embodiments, bracket 324 can be spaced or continuous.

It should be noted that any element in any of the above figures may be applied to and other of the above figures. Although the preceding is most applicable to a fixed mast, it can also be used with a rotating or partially rotating mast.

FIG. 4 shows a method of reducing the remaining boom loss shown by wind tunnel testing to be approximately 25%. A boat 400 with fixed mast 402 and spreaders 404 are shown as having an aerodynamic fairing 406, sail 408 and boom 416. Beneath boom 416 are two skirts 414A and 414B, surrounding yang 426 one being hidden behind the other. Skirts 414A and 414B, extend vertically from under boom 416 to close to deck (or top of a coach house) 421. Skirt or skirts each have at least one vertical batten, shown at 420, if skirts are cut diagonally as at 419.

Skirts 414A and 414B may have clear panels, one at 424 and skirt or skirts would be tensioned by an outhaul or outhauls, not shown. The front of skirts 414 are shown having two vertical furlers 430A and 430B hidden behind. These two furling tubes are in one embodiment, attached directly or indirectly to boom 416. Furlers can be manually, electrically or hydraulically operated to retract or deploy Skirts 414A and 414B horizontally. At the front of the skirts, furlers 430A and 430B is a fairing 432 which wraps around bottom of mast 402 to streamline mast and front of skirt furlers 430A and 430B. Note, a simpler but not as effective alternative is to use a triangular skirt with bottom shown dotted at 422 running directly from and elastically connection at bottom of mast 402 to near the outer portion of boom 416.

It would also be possible to have one skirt which wraps around the bottom of mast 402 having a double panel from the mast bottom to just behind the yang 426, which skirt is deployed and stowed or removed manually as required. Bottom of skirt 414 would need also need to be elastically tensioned in this case to allow for difference in tension by vertical movement of the boom 416. Further, top of skirt or skirts 414A and 414B could hang from loops over boom, or run in tracks under the boom 416 (neither shown).

One method of attachment of skirt 414 directly to bottom of mast 402 is for top most skirt fronts to be connected to mast bottom at 401 and cut on a diagonal so that bottom of front of skirts 414 wrap around each side of mast 402 shown by dotted diagonal line 433. In this arrangement, elastic tension would be maintained at each bottom corner 431A and 431B, so as to allow for horizontal movement caused by vertical adjustment of end of boom 416. Skirt or skirts may also be stowed by simply raising vertically and tying beneath the boom.

If skirts 414A and 414B are simple wraps around the mast as described above, they could alternatively be deployed or stowed by being part of a lazyjack system, raised by lazyjacks 410A and 410B to dotted position 412. Note diagonal rear of skirt 419, does not need to extend to mainsail tack, but may be shorter as shown at 419A, in which case batten would be positioned at 420A. To be effective in reducing the inefficiency of the mainsail due to under the boom losses, the skirt would need to block more than ˜35% of the distance from the mast to the clew of the mainsail. This skirt system as described above, being easily stowed and deployed, could be used when maximum efficiency or drive is required.

In small boats or dinghies, where maximum performance is desired, but a skirt would interfere with crew transfer from one side of the boat to the other during tacks, then clew of skirt could be collapsed, partially or fully, toward the mast during tacks shown by arrow 417. Optimally in this arrangement, the end of skirt or skirts 414A and 414B could be elastically tensioned in direction of arrow 417. Skirt outhaul would be released during a tack in order for skirt end or ends to retract to allow crew to cross under the boom, and then a skirt outhaul would be tensioned to deploy the skirt for efficient sailing, after tack is completed.

Shown at 404 is a spreader base which has a horizontal center well forward of the normal mast horizontal center, in order for the maximum rotation of the rotating sleeve and sail track proposed in this disclosure. Note also flexible wrap 406 is slotted a mast forestay and spreaders, to allow for rotation of the wrap assembly.

Alternatively, a single skirt could be employed under boom 416 if the single yang 426 is replaced by dual vangs, one on each side of boom 416. In this case, a rotating sleeve around mast 402 connected to the single skirt would be used. If a single skirt is used, a single vertical skirt furler could also be used in place of dual furlers of FIG. 5.

FIG. 5 shows a part cross section at 436 of FIG. 4. With mast section 502, boom part 505 and flexible mast wrap fairing 522, which all rotate around gooseneck 504 and mast 502. A yang portion is shown at 508. Under boom 505 and connected to it, is bracket 517 which pivots on boom 505 at 515. Twin vertical furling tubes are shown at 518A and 518B. Note, furling tubes may also be fixed and not rotating. Attached to furling tubes 518A and 518B are deployed skirts 514A and 514B, also shown at 414 of FIG. 4.

Air direction is shown by arrow 520. Flexible mast wrap 522, provides an aerodynamic fairing to allow air to flow around mast 505 and skirt 514A, depicted by arrow 507 causing the air thus flows smoothly around back side of skirt shown by arrow 507. This allows the arrangement to not only block the ˜25% under boom losses, but also adds to the drive of the mainsail.

A furling control mechanism could be attached to each furling tube 518A and 518B or could be a single mechanism housed between furling tubes, shown dotted at 516. Bracket 517 can alternatively be fixed so as to position furling tubes symmetrically about boom 505. Another alternative arrangement is to have one central skirt shown dotted at 512 and wrapping around mast at 519A and 519B, with an elastic lower portion to allow for boom movement.

For this single skirt arrangement, above, 512, 519A and 519B to be of maximum aerodynamic efficiency, there would need to be twin vangs, shown connected to each side of boom 505 dotted at 519A and 519B. With twin vangs, it is also possible to employ one furler positioned centrally at 516. It should be noted, all skirts would be of flexible material.

FIG. 6 shows a partial elevation of a boat 600 with fixed mast 602, traditional mainsail 608, traditional boom 624, and front pivot 639. Mainsail has clew outhaul 618. Mast 602 has an optional rotating sleeve and sail track shown dotted at 604. Note, the rotating sleeve connection may also be connected via a zipper shown partially dotted at 606.

A skirt 636 wraps around mast 602 with clew 624 of skirt 636 positioned on each side of boom, around yang, not shown. Skirt has top 617 close to bottom of mainsail 608, or even overlapping for maximum effect, shown dotted at 613. Skirt bottom 633 would be close to deck (or coach house top).

Skirt 636 has twin clews, one shown at 624 tensioned with outhaul line around pulley 620 and back along (or inside) boom. If skirt 636 is of one piece, wrapping around mast 602, in order for boom to move upward, skirt outhaul 620 needs to be elastic. This elasticity can be achieved by an elastic line, shown dotted at 632. Alternatively a spring or air cylinder could be used for tensioning. An alternative to an elastic skirt outhaul 632, is for a second boom for the skirt clew to be used, as shown at 625. This second boom, could be pivoted at 614. Secondary skirt boom 625 would be a separate boom 622. It could be of any cross section or be a channel as shown, dotted, surrounding bottom of boom 622. This arrangement allows main boom to pivot vertically upwards, with a non-elastic skirt or skirt outhaul.

-   Pivot of secondary skirt boom 625 is shown attached to main boom     622, but it's pivot 614 could be attached directly to mast 602

Foot of sail 616 is undercut at 614 so as to make foot of sail shorter than max chord 610 shown dotted, with batten 612. In this way a shorter skirt can be used so that combined skirt 636 and sail 608 eliminates the majority of the normal 25% foot loss under the boom 622. By providing a shortened mainsail foot, skirt 636 length, can also be reduced, allowing maximum clearance at the rear of the boat as well as a reduced boom length.

A batten 628 of skirt 636 is required to keep corner of skirt 630 from curling. Each side of skirt 636 can also be attached at 630. Skirt 636 could also be cut on the diagonal shown dotted at 634, to provide a partial reduction of the normal 25% foot loss. It should also be noted that one outhaul could be used if the main outhaul and skirt dews are attached to foot of sail 618.

When deployed, the skirts shown, offer a number of important advantages, it will reduce the height of the center of effort of the mainsail, which will reduce heeling. An added skirt will also not only block the traditional under boom losses, shown by wind tunnel tests to be approximately 25%, but if designed correctly as in FIG. 5, or as part of the mainsail as in FIG. 6 and if skirts are aerodynamically shaped, a skirt will add to the mainsail drive, and turn a traditional 25% loss into a ˜30% gain, due to the added drive. This in turn will further allow a smaller lighter mast, sail and boom, while at the same time adding significant performance and easier handling.

It should be noted that the skirts shown above need not block the space below the boom completely, but to be effective should block at least 25% of the area between the boom and deck, or coach house. It should also be noted that any element in the above FIG. 4, 5 or 6, may be applied to any of the other FIG. 4, 5 or 6.

In order for the rotating mast sleeve shown above to be of maximum effect, the track and head of the sail must be able to rotate, FIG. 7 shows part view of a mast top 700 with oval mast 701. A rotating mast sleeve 716 with bolt rope sail track 718 and attached mainsail 720. A halyard 710 is attached to sail head at 714. Halyard passes over a sheave 706 and down inside mast 701 at 712. Sheave 706 is held in an arm 708 rotating in a bracket 702, which is fixed to mast, one point of attachment being 722. Bracket arm 708 pivots in bracket 702 at 704. Pivot 704 and bracket 702 are positioned as shown so that halyard 710 allows head of sail, sail track 718 and sleeve wrap 716 to rotate around the oval mast 701 in order for the maximum airfoil shape of the sleeve and sail to be achieved on the lee side.

FIG. 8 shows another method of achieving a rotating mainsail head with an alternative mast top configuration 800 having mast 801, rotating sleeve wrap 808 sail track 812 and sail 814. Head of mast 801 is undercut at 804 and 804A so that halyard sheave 802 is positioned near the center of mast 801 rear radius to allow halyard 806 connection 810, sail track 812 and sail head 814 to rotate freely as required. In this way, sleeve 808 and sail 814 is able to form an optimal aerodynamic shape on lee side of mast 801.

FIG. 9 shows another method of achieving a rotating mainsail head with an alternative mast top 900 having mast 902, rotating sleeve wrap 910, sail track 911 and sail head 912. Top portion of oval mast 902 is circular and carries loose rotating bracket 904. Attached to end of bracket 904 is a block or sheave 906 a halyard 907 is attached to head of sail 912 at 908. Halyard runs through block or sheave 906 and down within sleeve shown dotted at 907A. In this way sleeve 910, sail track 912 and head of sail is able to rotate as required for maximum sail efficiency.

FIG. 10 shows another method of providing a mast top halyard connection. Mast top 1000 has an oval mast 1001, rotating sleeve wrap 1018, sail track 1016 and sail head 1014. Attached to mast top 1001 is a bracket 1004, affixed to mast at two points, one shown at 1002. Slidably attached to bracket 1004 is a halyard block 1006, which is able to slide horizontally around bracket 1004.

Sail head 1014 has a halyard attached at 1010 which passes through block 1006 and down inside sleeve 1018 shown dotted at 1012. Bracket 1004 could also be of soft material or rope, attached to points, one shown at 1002. An alternative soft loop shown dotted at 1020 could also be used in place of 1004, with loop 1020 surrounding mast 1001 and held by side brackets, one shown at 1022. In this way sleeve 1018, sail track 1016 and head of sail is able to rotate as required for maximum sail efficiency.

FIG. 11 is yet another method of providing a sail head and halyard connection which allows rotation of sleeve wrap and sail. A mast top 1100 is shown having an oval mast 1102 with rotating sleeve wrap 1120, sail track 1115 and sail head 1114. A typical halyard 1106 and halyard sheave is shown at 1104. Two brackets are attached to each side sail head shown at 1110 and 1110A, with one attachment point at 1112. Brackets 1110 and 1110A are spaced apart at their top most portion. Attached to the top of these brackets 1110 is a shaft or tube 1108, running perpendicular to sail top 1114 as shown. H

End of halyard 1106 is attached loosely to shaft or tube 1108 so that a reasonable rotation of sleeve 1120 and sail head 1114 is possible to achieve high aerodynamic efficiency of the mainsail. It is even more important for maximum aerodynamic efficiency that the tack of a mainsail according to the present invention is not fixed.

FIG. 12 shows 1200, being a part section of a mast 1202 and boom 1218 of a traditional yacht. Also shown is a rotating sleeve wrap 1204, sail track 1206 and sail bottom 1210 with tack eyelet 1208. A gooseneck assembly is shown at 1230. Attached to boom are two brackets, shown at 1214 and 1214A. Attached to top of brackets 1214 and 1214A is a shaft or tube 1212 perpendicular to boom 1218. Bottom of brackets 1214 and 1214A are attached to boom 1218 tightly, or so as to allow bracket to pivot. A second tube or shaft 1215 could alternatively be used through boom 1218 attached to bottom of brackets 1214 so as to allow tubes and brackets to move side to side shown by arrow 1220. Note brackets 1214 could also be soft and flexible connectors.

It would also be possible to connect ends of rod or tube 1212 to lines shown dashed at 1224 and 1224A directly to base of mast 1202. (these lines one shown dotted at 1221 could also pass through brackets on each side of boom shown at one at point 1216). An alternative would be to connect lines 1224 and 1224A to a single line 1228, passing through mast base block 1226, so as to be able to adjust tension in lines 1224 and shaft or tube 1212. Note tack hole 1208 is larger than rod or tube 1212 so that tack is able to slide sideways along rod or tube 1212. In this way, sail tack 1208 is able to slide side to side along rod 1212 allowing sleeve 1204 tack 1208 and sail track 1206 to rotate in order for foot of sail 1210 shown by dashed lines, to achieve the maximum aerodynamic efficiency.

FIG. 13 shows 1280 being view of a partial mast 1252 and boom 1273 detailing how a rotating sleeve wrap according to the present invention can be applied to a mainsail boom furling system.

Mast 1252 has section of fairing wrap 1254 with partial sail track 1256 and part sail 1258, together with traditional boom 1273 connected to mast with traditional gooseneck assembly 1279. A mainsail boom furling tube 1264 has a manual turning sheave 1259 which with a line, not shown can be used to furl mainsail. Furling tube 1264 is held at each end by brackets 1262 and 1268, through which shafts 1276 and 1266 pass. These shafts can pass through spherical ball joints within housing brackets 1262 and 1268, or as shown, could have pivoting housings 1260 and 1272 pivoting on housing brackets 1262 and 1268. Shaft 1266 is able to slide in housing (or spherical bearing).

Bracket 1268 is fastened to boom 1273 as shown. Two brackets, one visible at 1278, holds a cross rod or tube 1276 on which housing 1262 slides, shown by arrow 1275. In this way, sleeve wrap 1254 together with sail track and sail 1258 is able to rotate around mast 1252 to allow a highly efficient aero foil shape to be produced on the lee side of the mast at the lowest portion of the mainsail, thereby producing maximum drive from the foot of the sail, if a skirt is employed to eliminate the otherwise lost drive from under the boom.

FIG. 14 shows another method of attachment of a mainsail tack allowing rotation of the sleeve wrap and sail according to the present invention. Part sail tack and boom detail 1400 shows a mainsail corner 1410 with tack eyelet 1406. Eyelet connects to a forward pointing right angled rod or tube 1414 via a shackle or rope loop 1408. Note a loop sewn to sail would also be possible. Vertical shaft portion of rod or tube 1414 passes loosely through vertical hole 1415 of boom portion 1412. End of rod or tube 1414 could be terminated under boom 1412 at 1416, or be attached to a tensioning line similar to line 1228 of FIG. 12. Rod or tube 1414 could also be housed in gooseneck vertical pivot hole shown by centerline 1418 or position 1418A and point rearwards. Right angled rod or tube 1414, could terminate under gooseneck or be attached to a line for vertical adjustment. In this way, mast wrap 1401, sail track 1404 and sail corner 1410 is able to rotate, via rotation of right angled shaft or tube 1414 shown by arrow 1417 as required to achieve the maximum aerodynamic efficiency at the back of the mast at the foot of the mainsail according to the present invention. Note, loop or shackle 1408 would slide along rod or tube 1414 during the rotation of rod or tube 1414.

FIG. 15 shows a partial cross section 1500 of a mast segment 1502 and a sail track 1516 which is connected to a flexible wrap around mast 1502 the ends of which are shown at 1504 and 1520, attached to sail track 1516 at 1805 and 1518. Spaced multiple elongate cars or slugs are shown cross sectioned at 1514 are connected to multiple elongate spaced members shown shaded at 1508, via loose rivets or bolts shown at 1512, such that when sail is lowered, members 1508 are able to rotate to approximately the horizontal position for flaking. Mainsail portion 1506 is connected to spaced members 1508, by any means, one of which being wrapped around members 1508. At 1510. Member segments or padding can be used between spaced slugs or cars 1810 to avoid a large gap between short elongate members 1508, in order that minimal air from the windward side leaks into the lee side of the sail. Note, wrap 1504/1520 may be short and separate bands, or run the length of the track 1516.

In this way car type slides may be used, which gives better control of the sail when lowering, while still providing a good airfoil connection on the lee side of the sail to mast, in order to give maximum aerodynamic efficiency and drive and eliminate the majority of the approximately forty percent loss of the normal car type mainsail to mast connection. The above show means to significantly increase the efficiency and drive of a mainsail while at the same time allowing for a smaller sail with a reduced center of effort producing less heel and much easier sail and boat handling in strong winds. The arrangements detailed would also significantly reduce drag and weight of a yacht. It should be noted that the foregoing improvements or details of one arrangement may be, where appropriate, applied to any of the other arrangements.

It should be noted that although mainsails are the predominant form of mast sail combination, the above disclosure applies equally to other mast sail combinations such as mizzenmasts and sails. 

1. A sail attached indirectly to a fixed mast, the sail comprising: a rotating flexible mast sleeve wrap surrounding the mast and attached to a sail track for controlling the movement of the sail, wherein the sleeve assembly is slotted to allow for partial rotation of the sleeve wrap, the sail track and the sail, so that the sleeve wrap, the sail track and the sail can rotate to form an aerodynamic shape on the lee side of the rotating flexible mast reducing aerodynamic losses.
 2. A sailing boat with a mast and boom, wherein the majority of the open space between the boom and deck or coach house has a skirt extending horizontally from the mast to more than half-way to the mainsail end or clew, wherein the skirt reduces the majority of the otherwise loss of efficiency and drive under a traditional boom.
 3. The sailing boat of claim 2, wherein the skirt wraps around the base of the mast so that there are two skirts behind the mast.
 4. The sailing boat of claim 2, wherein the skirt allows for vertical movement of the boom end.
 5. The sail of claim 1, wherein the mast sleeve wrap and sail track assembly house a vertical furling tube assembly for vertically furling the sail.
 6. The sail of claim 1, wherein a tack of the sail is not fixed but allows for the partial rotation of the sail tack area, so that sleeve wrap, sail track and sail tack rotate to form an aerodynamic shape on the lee side of mast at the foot of the sail, reducing aerodynamic losses at the foot of the sail.
 7. The sail of claim 1, wherein the fixed mast has non-circular cross section, having a substantially semicircular-shaped rear radius and a front radius smaller than the rear radius.
 8. The sail of claim 1, wherein a root of a spreader has a horizontal central point which is forward of the front to back center of the mast section to allow for maximum rotation of a rotating sail track or vertical furling system.
 9. A sailing boat of claim 2 where a skirt is furled by at least one vertical furling tube behind the mast and predominantly below the boom. 